Photographic tone correction mask



June 12, 1945. P. K. GLASOE 2,378,213

PHOTOGRAPHIC' TONE CORRECTION MASK Filed Jan. 7, 1944 @MKG/060@ W, JWM

@Patented .im 12,- 1945 UNITED', STATES 'PATENT AOFFICE:A

y 2,318,213 Pnoroonarmo TONE CORRECTION Mask Paul K. Glam,'nocnester, N. Y., asignar to Eastman Kodak Company, Rochester, N. Y., a corporation of Nev Jersey Application January 7. 194,4,seria1 No. 517,392, v`

(o1. ss-z) 12 Cmms.

I subtractive color photography, onto a material .to

vbe processed by reversal, the low contrast in the highlight regions is exaggerated by being printed onto the low contrast highlightregions of the reversallmaterlal.

Also, in printing from multicolored originals which consist in whole or in part of dyes, the fact that the light absorption of the dyes lis extended to the whole spectrum rather than to one part ot the spectrum makesl it impossible to Obtain printed records of the individual dyessimply by restricting the vcolor of the printing light. Since in most three-color photographic processes the three dyes are not equally bad in this respect, the nal result of printing such a nlm is to introduce unequal 'parts of all three records in eachimage .which ismade, regardless of the color of light used in printing orthe sensitivity of the photo- .graphic materials used.

In order, to compensate for the denciencies of the dyes used in such processes, negative color correction masks are prepared by exposing a suitably sensitive emulsion layer through the' multicolor originals with a selected exposing iight and forming a metallic or colored image' of the exposed layer which, when placed in registry with the original during printing effects color correction. Typical methods oi preparing such Amasks are described in Evans United States Patent No. 2,203,653, granted June 4, 1,940, Hanson United States Patent No. 2,294,981, granted Sellteinbel 8, 1942. Evans United States patent application.

Serial No. 413,442, filed October 3, 1941,"and elsewhere.

In fthe present application I describe 'a method j' ot preparinga color correction mask which not onlyfcorrects for the deficiencies of the subtractive dyes of the color process, but also has tone reproduction characteristics such that when a print is made from the combination of the mask with the original transparency of which the mask is a record, large improvement inthe tlnal 4tone reproduction of thetransparency is achieved in the print or duplicate.

One object of the present invention is to'provide a tone correction mask of use for improving v me reproduction during the printing of images having improper tone reproductioncharacteristics.

se Another object ofthe present invention is to provide a tone correction mask of use in black: and-white and color photography for improving tone reproduction during printing from blackand-white or colored images having improper' tone' reproduction characteristics. y

Another object of the -present invention, and

the preferred embodiment thereof. is to prpvide a tone and color correction mask of use in color photography for improving the tone reproduction and color during printing from colored images.

In general, the Objects of my invention are accomplished by forming in a photographic emulsion layer an imageof opposite sign to a transparency having improper tone reproduction characteristics. of which it is a record, the characteristic curve of the.image being such that when the image is combined with the transpar- 'encyan improvemen in'` tone reproduction is achieved, f

In the ligure ofthe accompanying drawing are shown by graphical representation the characteristic curves of variousphotographic elements employed inmy invention.

In the ngure of theaccompanying drawing,-

curve M represents the 'characteristic curve of an image obtained by lowintensity exposure through -a color transparency having a reproduction curve such as curve T. Curve acteristic curve of an image obtained by exposure through the transparency onto the unex-A v transparency having a reproduction curve such as curve T of the drawing.

In the normal procof reproducing this transparency, as for instance, onto a multi-color reversal process of color photography employing color-forming development, there would be obtained a print in the toe region of which the low contrast of the toe of the curve T would be exaggerated. This is-true whether or not the usual color correction mask is employed in the printing process.- However, if in the manner of my invention another characteristic-be impartedto the .color correction mask, the errors of tone reproduction are partially or completely compensated for. A mask of these characteristics is prepared as follows:l

commonly used'on positive motion picture iilm,

Mi represents the charlmbymeansofthea nlm carrying an emulsion such 'as Borax ferent developing solutions and highly sensitive to a region of the spectrum such as red, green. or

instance, to red light has been destroyed. the film is resensitized in a suitable sensitisim bath l of the following Icomposition:

.svaais Pinacyanol .gram...V Alcohol (commercial 3A) .'..cc.' "l5 Pyridine vc 1 Benzotriazole -i -gram.- 0.1 Water to -.'----..liter-- 1 It is apparent'that in the above steps one may start with an ordinary blue-sensitive nlm and sensitize it. for instance. to red light at the startins with a nlm sensitive o only to blue light but to'red. green. or yellow g t. The film is then washed and dried land followingthis itisgivenasecondexposurewithred light throughthe transparency so as to record all of the detail of the ncy. This exposure may be made to a nlter such as 'wratten No. 25 filter. Following this the nlm is developed atl 'l0' F. for about six minutes to a gemma ot about 0.5

in a developer of the followinz composition:

Sodium suliite ..-grams p-Methyl amino-phenol sulfate .--.do`-.s.. Bydroquinone'---....,------1..-..-..

. "n 2- Water to .,...........liter. 1' nnalmhesimnnxedwuhedandaried. 'rias procedure gives a mask havin! a' low gamma nega tive curve and a sharp in curve Mi of the higher exposure as shown drawing. -Generally.agammaoitheranaeotthe order of from 0.8 to 0.8 is satisfactory for this imosaondtheratiooitbeganrngoi point Potassium i'erricyanide ..-grams- Potassium bromide do-- 20 water to mehr 1 the gamma of the above hih-'gamma image is. therefore. of the order of 1/0.6 to 410.3. Thehig'her the ratio selected the greater thev correction irnparted to the transparency. The mask thus ob' yellow (this sensitivity being chosen for the par- 5 tained has substantially the characteristics shown ticular color correction desired) is,l for instance. by curve Mi of the drawing. wherein the straightexposed through the transparency having the lineportion of the curve is a low gamma image characteristics shown in curve T with blue light havingodensity variations of opposite sign tothe (wratten No. 47 filter) so that substantially only transparency having curve T, and the shoulder or those densities of the transparency below`0.8 are high density region is a positive with respect to recorded. The film is then hardened in a formalthe transparency T. Since the mask is a positive dehyde hardener solution and developed to a high in the shoulder region it may be said to have no contrast in a developer o f the following compodensity variations of opposite sign to the density sition: variations of the transparency in that region.

. An alternative procedure in obtaining the commmiiiiiimo- 2` man com @www and. me www sdmm hydroxide man 37.5 mask according to my invention Ais to rehalosenlze Potassium mamme don" so the first-developed silver. without-removing it Water ,n met 1 prior to the exposure of the residual silver halide. 20 lThe mst-developed silver may be bleached to sil- Followins development. the film is Whd and ver bromide in a potassium' ferricyanide-potasdried without fixing. 'The imale contained thoreslum bromide solution which converts the devel. i in has Substantially the hl`nr18ti8 IhOWn by oped silver to silver bromide. 'The silver bromide curve M of the drawing. For use with most color thus formed is apparently greatly desensitized so transparencies. n smm 0f the' IBN@ 0f 311 25 that upon second "exposure of the film using red order of 1 to 4 is satisfactory for this imno. light very little silver is formed in the'rehaloiien- After development the developed image' il ized region. bleached in an acid bi'chromate bath followed by The following example illustrates the method of a wash in ammonium hydroxide solution. The using my rehaloenizationprocedure. ammonium hydroxide solution lsmnde b! dilute After exposure o f the positive tllm through the ing l0 cc. of concentrated ammonium hydroxide pareney with blue light as described above to 1 liter. The biehromate solution has the i01- t emulsionis developed in a high contrast delowing composition: f veloper which may' have the following composi- Potassium blchromate u--.. ..-.t....-..-grams.". 5- 15F v j sulfuric acid (concentrated) do 5 35 sodium sulphitegrams-- Water to 111217-- 1 Hydroqulnone .do. l0

' Sodium carbonate --do..;-- .Tmpgggggggg ggfs-m im @mi 1" v am ...gag g f tassium rom e 0.--- At this point it the sensitivity of the nlm. for 40 water to 5 mer" 1 for 4 minutes- The silver image thus formed is bleached for 4 minutes in the following solution and washed for 4 minutes:

The emulsion ls then4 exposed through the transparency to naught and developed for e `minutes in the second developer described above' or in the following developer:

Sodium sulphlte ..srams-- Paramethyl amino phenol sulphatem 1 Hydroquinone -do.---, 5 Borax 'do v3 Potassium bromide .Y do-- 0.25 Water to -....--.liter-- l from the orlsinal. .70

From 50 to 100 mg. per liter of bensotrlanole -may be added to this developer to inhiblt'development of the rehalosenlzed silver.

s The required contrast can be obtained ing the time o! development in the second developer.

4 In order to print color an dtone corrected prints.

transparency. the mask is placed transparency. prints beine A in registry with the 4made on a suitable multilayer color film in a processsuchasdisclosedinusnnesetahnited l states Patent 2,252,718, granted August 1 9, mi,

or if desired. color separation records may be thisimatet-iprintedandmedin known color processes.

this solution records only Y tion having characteristics shown by curve M1. in order to compensate forV low contrast in the highlight portion of a trans- EEST VILBE COPY As shown by curve T1 of the drawing, the reproduction curve of the combination oi! the transparency and the mask is greatly improved. -Not only has the mask eiected an overall decrease in contrast in the reproduction curve, but in the'low density region corresponding to the highlights of thetransparency, the contrast has been raised so that constant contrast is obtained throughout the length of the characteristic curve.v Of course, since the exposing light for the exposure of the final mask is preferably selected so as to compensate for the errors in absorption of the dyes used in the process, color correction is-also aiiected. The choice of wave length of vexposing light de-` pends upon whether orwhat correction is desiredf especially substantially monochromatic yellow light, chosen according to the principles laid down in the prior United States Patent 2,294,981 issued September 8, 1940, above-cited. As above-mentioned the mask of the inven-y substantially as parency, must have little or no gradationin the shoulder region with respect to the transparency. In curve M1 the mask is shown 'as having decreasing density, i. e.positive density gradient in the shoulder region to compensate for the low contrast in the toe of the transparency curve T.

ln printing in combination withv the image of which it is a'record of opposite sign, an improve tering the overall contrast in thel print but obfor errors in tone of taining some compensation the original.

In addition, my inventionmay be used in conjunction with 'printing from a colored lnegative transparency, as for example, prepared from photographic elements designed as described in Jelleyf and Vittum United States Patent 2,322,027, granted -June l5, 1943, Mannes et al. United States Patents 2.304,939and 2,304,940, granted December 15, 1942, that is, in conjunction with Q coloriilms which after original exposure areim'- I contemplate as within my invention tone and color correction masks of the general characteristic described, wherein the straight line portion of the .characteristic-curve is negative to a transparency of which it is a record, and in which in the shoulder region there is little'or no gradation of opposite sign to the transparency,

but including density variations of -the same sign in that region. Therefore, herein and `in the appended claims where I state that the mask has 'in the shoulder region no appreciable density variations of opposite sign to the density variations of the transparency, I mean it to be understood that this includes inthe shoulder region:

l (1) small density variations of opposite sign to the transparency but of an order'less than normally obtained with photographic emulsions,

(2) no density gradation in the/portion or the shoulder masking the toe of the transparency, f

and (3) density varying in the same direction as the density variations of the transparency.

Another use for which the mask of my invention is especially adapted, is in projecting or viewing of color transparencies. That is, in reversal processes of color photography where colored images are formed by means or color-forming development, images are obtained common-f ly having high contrast and tthe usual low con-` trast in the shoulder and toe regions (see curve T). A mask prepared'as described is especially suitable for combining with such a transparency 'when it is desired to obtain the best image for mediately developed to subtractively colored dye images. In this case, the nal mask is a nega-` tive record of the color negative but, of course. is a positive with respect to the nal positive color print. In fact, my invention is applicable to the improvement of ltone reproduction any process of photography wherein the image of which the mask is a record has tone reproduction errors of the vorder described. Vi i Also apparent, is the fact that the masks of my invention4 may be designed so'as to correct not nly for tone reproduction errors .of the transgarency being printed, but also to correct forV tone reproduction errors introduced by the duplicating process. This is accomplished by giving the mask a shoulder gamma compensatingV for tone'errors of boththe toe of the transparency.

andany toe introduced in the duplicating process. I

My invention ,having thus been described I would haveA it understood .that the disclosure herein is by way of example, and that I consider as included in my invention all modifications and equivalents falling within thescope oi' the appended claims. I l

What I claim is:

1. The method of forming a photographic tone correction mask which comprises giving a lights'ensitive silver halide emulsion layer an exposure through a-transparency of such intensity' that only the toe densities of said transparencies are recorded, developing in the exposed emulsion layer a silver image of opposite sign to said transparency and of higher gamma than a secondv image subsequently formed therein, converting said silver image 'to a transparent form inactive with respect to subsequent exposure and development of unexposed silver halide in said layer, exposing the emulsion layer containing unexposed silver halide through said transparency to record all oi the detail of said transparency, forming in the exposed emulsion layer an image of gamma lower than said first-mentioned silver image and removing all silver halide from the emulsion layer.

-2. A method of forming a photographic tone correction mask which comprises giving a lightsensitive silver halide emulsion layer an exposure through a transparency of such intensity that only the toe densities of said transparency are recorded, developing in the exposed emulsion layer a'silver image of opposite sign to said transparency and of higher gamma than a second image subsequently formed therein, removing said image `from the emulsion layer, exposing the Y emulsion layer containing unexposed silver halide through said transparency to record all or the detail of said transparency, forming in the exposed emulsion layer an image oi gamma lower than said first-mentioned silver image and re moving any unexposed silver halide from the emulsion layer.

3. In a process of printing a color transparency in natural colors the method of forming a photographic tone and color correction mask which comprises giving a light-sensitive silver halide emulsion layer an exposure through a color treinsparency oi'such intensity that only the toe densities of said transparency are recorded, developing in the exposed emusion layer a silver image of opposite sign t said transparency and oi higher gamma than a second image subsequentlyv g formed therein, removing said' image fromy the emulsion layer. resensitizing the Vremaining sliver halide and exposing the emulsion layer containing unexposed silver halide through said transparency to record all of the detail of said transparency, forming in the exposed emulsion layer an image of gamma lower rthan said first-mentioned silver image and removing any unexposed silver halide from the emulsion layer.

` 4. In a process oi printing a color transparency in natural colors the method oi forming a photographic tone and color correction mask which comprises giving a light-sensitive silver halide emuisionclayer an exposure through a color transparency of such intensity that only the toe densities of said transparency are recorded, developing in the exposed emulsion layer a-'silver image ci opposite Slim to said transparency and of higher gamma than a second image suhsequent.

variations of a transparency of which it istafy record ,and in the shoulder portion n0 appreci- ,able' density variations of opposite sign the density variations of said transparency. E 5. In a processo! printing a color ltransparency graphic tone and color correction mask which comprises giving a light sensitive silver -haiide emulsion layer an exposure through a positive color transparency of such intensity that only the toe densities oi said transparency are recorded, developing in the exposed emulsion layer a silver image oi opposite sign to said transpar- .ency and of higher gamma than a second image subsequently formed therein, removingsaid silver emulsion layer containing unexposed silver halide through said transparency to record all ci `the detail of said transparency. forming in the exposed' emulsion layer an image of gamma lower than said first-mentioned silver image and removing any unexposed silver halide from the emulsion layer, said last-formed image 'being of s opposite sign to said transparency in the straight- Aline portion of its characteristic curve and of the same sign as said transparency in the shoulder portion oi its characteristic curve.

6. In aproceu oi printing a color transparency in natural colors the method oi forming a photoin natural colors the method of forming a photographic tone and color correction mask which comprises givinga light sensitive silver halide emulsion layer an exposure through a positive transparency of such intensity that only the toe densities of said transparency are recorded, developing in the exposed emulsion layer a silver image of opposite sign to said transparency and it higher gamma than a second image subsequentlyv formed therein, removing said silver image from the emulsion layer, resensitiaing -the remaining silver halide and exposing the emulsion layer containing unexposed silver halide through vsaid transparency to record all of the detail of said transparency with light of wave lengths which will correct for the inaccuracies in absorption of light by the dyes used in the process, forming the exposed emulsion layer an image of gamma lower than said mst-mentioned silver image and removing unexposed silver halide from the emulsion layer, said last-formed image being of opposite sign to said transparency in the straight-line portion of its characteristic curve and of the same sign as said transparency in the shoulder portion of its characteristic curve.

1. In a process of printing a color transparency in natural colors the method of forming a photographic tone and color `correction mask which comprises giving a light sensitive silver halide emulsion layer an exposure through a positive color transparency of such intensity that only the 'toe densities of said transparency are recorded with blue light, developing in the exposed emulsion layer a silver image o! opposite sign to said transparency and of higher gamma than a second image subsequently formed therein, removing said-silver imageirom the emulsion layer, resensitizing the remaining silver halide and exposing the emulsion layer containing unexposed silver halide through said transparency with red light to record all of the detail oi said transparency, forming in the exposedemulsion layer an image lof gamma lower than said first-mentioned silver imageand removing only unexposed silver halide from the emulsion layer, the gamma of the iirst-formed silver .image being oi a range of the order of l to 4 and the gamma oi said last-formed image being oi a range oi the order of 0.3 to 0.6. i l 1 8. In a process oi printing a color transparency in natural colors the method of forming a photographic tone and color correction mask which comprises giving a light sensitive silver halide emulsion layer an exposure through a negative transparency of such intensity that only the toe densities oi' said transparency are recorded, developing in the exposed emulsion layer a silver image of opposite sign tov said transparency and of higher gamma than a second image subsequently formed therein, removing said silver image from the emulsion layer, exposing the mulsion layer containing unexposed silver halide l image from the emulsion layer, exposing the through said transparency -torecord all of the detail of said transparency, forming in the exposed emulsion layer an image of gamma lower than said mst-mentioned silver image and removing any unexposed silver halidefrom' the emulsion sian as said transparency in the sian to said transparency in the straight-linefportion of its characteristiccurve and of the same shoulder portion oi its characteristic curve. l

9. In a process of printing a color transparency in natural colors the method oi' forming a photographic tons and color correction mask which' asvaaia comprises giving a light sensitive silver halide emulsion layer an exposure through'a negative gamma o! the mst-formed silver image being oi' a color transparency of such intensity that only the toe densities of said transparency are recorded, developing in the exposed emulsion layer a silver image of opposite sign to said transparency and of higher gamma, than a second image subsequently formed therein, removing said silver image from the emulsion layer, resensitizing the remaining silverphalide and exposing the emulsion layer containing unexposed silver halide through said transparency to record all of the detail of said transparency with light of wave lengths which -will correct for the inaccuracies in absorption of light by the dyes used in the process, forming in the exposed emulsion layer an image of ,gamma lower than said first-mentioned-silver image and removing any unexposed vsilver halide from the emulsion layer, said lastformed image being of opposite sign to said transparency in the straight-line portion of its characteristic curve and of the same sign as said transparency in the shoulder portion of its characteristic curve.

10. In a process of printing a color transparency in natural colors. the method of forming a photographic tone and color correction mask range oi .the order of 'l to 4 and the gamma of said last-formed image being oiV a' range of the order of 0.3 to 0.6.

11. The method of forming a photographic tonecorrection mask which comprises giving a light-sensitive silver halide emulsion layer an exposure through 'a transparency of such intensity which comprises giving a light sensitive silver halide emulsion layer an exposure through a negative color transparency of such intensity that only the toe densities of said transparency are recorded with blue light.' developing in the exposedemulsion layer a, silver image of opposite sign to said transparency and of higher gamma than a second image subsequently formed therein, removing said silver image from the emulsion layer, resensitizing the remaining silver halide `and exposing the emulsion layer containing unexposed silver hailde through said transparency with red light to record all of the detail of said transparency, forming in the exposed emulsion layer an imagel oi' gamma lower than said iirstmentioned silver image and removing any unexposed silver halide from the emulsion layer, the

that only-the toe densities of said transparencies art recorded, developing in the exposed emulsion layer a silver image ofopposite sign to said transparency and of higher gamma than a second image subsequently formed therein, converting the developed silver to silver bromide inactive with'respect to subsequent exposure and developtone correction mask whichlcomprises giving a light-sensitive silver halide emulsion layer an exposure through. a transparency of such intensity that only the toe densities of said transparencies are recorded, developing in the exposed emulsion layer a silver image of opposite sign to said transparency and of higher gamma than a, second image subsequently -formed therein, converging the developed silver to silver bromide in a, ferricyanide-bromide bleach bath, said silver bromide being inactive with respect to subsequent exposure and development of unexposed silver hal ide in said layer, exposing the emulsion layer e containing unexposed silver halide through said transparency to record all of the detail or said transparency, forming in the exposed emulsion layer an image of gamma lower than said iirstmentioned silver image and removing all silver halide from the emulsion layer.

Y PAUL K. GLASOE. 

